#4 Oxidative stress and lipid peroxidation Flashcards
(20 cards)
What is oxidative stress?
An imbalance favoring prooxidants over antioxidants, leading to disrupted redox signaling, control, or molecular damage.
What are prooxidants?
Molecules that promote oxidation, including free radicals (like hydroxyl and superoxide) and non-radicals (like hydrogen peroxide).
How does radical half-life affect reactivity?
The shorter the half-life, the more reactive the radical.
What are some endogenous sources of ROS?
Mitochondria, enzymatic reactions, and peroxisomal metabolism.
What are some exogenous sources of ROS?
UV radiation, cigarette smoke, air pollution, and heavy metals.
What is the Haber-Weiss reaction?
Superoxide + H₂O₂ → OH● + O₂ + OH⁻
What is lipid peroxidation?
The oxidative degradation of lipids, leading to membrane damage and toxic byproducts like malondialdehyde (MDA).
What structural change occurs during lipid peroxidation initiation?
The lipid rearranges into a conjugated diene.
How do ROS affect proteins?
They can damage amino acids, increase proteolysis, and trigger protective modifications like glutathionylation.
What are the consequences of DNA oxidation?
Mutations, cancer initiation, energy depletion (via PARP activation), and error-prone DNA repair.
What are some examples of antioxidant defenses?
Water-soluble: Glutathione, uric acid
Lipid-soluble: α-tocopherol, coenzyme Q
Enzymes: Superoxide dismutase (SOD), glutathione peroxidase
How can oxidative stress be prevented?
Avoid environmental risks (e.g., smoking), use metal chelators (e.g., transferrin), or inhibit prooxidant enzymes (e.g., NADPH oxidase inhibitors).
What is the role of sacrificial antioxidants?
They neutralize radicals by forming stable products, e.g., LOO● + NO● → LOONO.
What is EPR (Electron Paramagnetic Resonance)?
A highly sensitive method for detecting and measuring free radicals.
What is the TBARS assay?
A test that measures MDA, a marker of lipid peroxidation, though less reliable for complex biological samples.
What diseases are associated with oxidative stress?
Cancer, atherosclerosis, inflammation, ischemia/reperfusion injury, and aging.
How do ROS contribute to cancer development?
ROS cause DNA mutations (initiation) and promote further oxidative damage (promotion).
